drm/i915/audio: fix check for av_enc_map overflow

commit 72a6d72c2cd03bba7b70117b63dea83d2de88057 upstream.

Turns out -1 >= ARRAY_SIZE() is always true. Move the bounds check where
we know pipe >= 0 and next to the array indexing where it makes most
sense.

Fixes: 9965db26ac05 ("drm/i915: Check for fused or unused pipes")
Fixes: 0b7029b7e43f ("drm/i915: Check for fused or unused pipes")
Cc: <stable@vger.kernel.org> # v4.10+
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180214173840.25360-1-jani.nikula@intel.com
(cherry picked from commit cdb3db8542d854bd678d60cd28861b042e191672)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
index 49af0034df19f901ed89b9d17866cd50b761b866..538a762f7318834ead3340a1b92baa4387d6fad1 100644 (file)
--- a/drivers/gpu/drm/i915/intel_audio.c
+++ b/drivers/gpu/drm/i915/intel_audio.c
@@ -754,11 +754,11 @@ static struct intel_encoder *get_saved_enc(struct drm_i915_private *dev_priv,
 {
        struct intel_encoder *encoder;
 
-       if (WARN_ON(pipe >= ARRAY_SIZE(dev_priv->av_enc_map)))
-               return NULL;
-
        /* MST */
        if (pipe >= 0) {
+               if (WARN_ON(pipe >= ARRAY_SIZE(dev_priv->av_enc_map)))
+                       return NULL;
+
                encoder = dev_priv->av_enc_map[pipe];
                /*
                 * when bootup, audio driver may not know it is